Wal Sargent was the first person from his high school to attend a university. He studied fluid mechanics at the University of Manchester, but with an eye toward applying it to theoretical problems in astrophysics. He spent nearly all of his career at the California Institute of Technology, where he became a spectroscopist, observing peculiar stars, stars in the galactic halo, and peculiar galaxies and quasars. He was particularly renowned for investigations of quasar absorption lines, which he observed with the Keck, Magellan, Chandra, and Hubble Space Telescopes. He and his colleagues contributed greatly to our knowledge of the intergalactic medium. As director of the Palomar Observatory from 1997-2000, he supervised use of the Hale Telescope to conduct the Norris Survey of large-scale structure in the distribution of galaxies at moderate redshifts, and he used the Samuel Oschin Telescope to conduct the Second Palomar Observatory Sky Survey. His surveys of active galactic nuclei produced evidence that many contain massive black holes. He also worked on the isotropy of the universe by studying angular fluctuations in the cosmic microwave background radiation. Renowned as a teacher and mentor, he was the Ph.D. advisor of a number of noted astronomers, including Alex Filippenko, John Huchra, John Kormendy, Bob O'Connell, Patrick Osmer, Charles Steidel, and Ed Turner.